Transmission input clutch

ABSTRACT

Clutch mechanism for coupling an engine to a transmission of the form in which ratio gears are decoupled from both the driving and driven shafts and braked to a stop to facilitate shifting has epicyclic gear means for imparting a predetermined slow rotation to the ratio gears just prior to full recoupling of the ratio gears to the driving engine and driven load. This assures that all necessary gear engagements are accomplished smoothly and without damage prior to the re-application of full torque load to the transmission.

United States Patent [191 Appl. No.: 217,784

Herr [4 1 June 5, 1973 54] TRANSMISSION INPUT CLUTCH 3,354,729 11/1967Marquart ..74 74o x Inventor: Charles H. Peoria, 1. 3,396,610 8/1968Rlch, Jr. et al. ..74/740 [73] Assignee: Cater pillar Tractor Co.,Peoria, 111. Pri ar ExaminerArthur '1. McKeon [22] Filed, Jan 14 1972Attorney-Donald J. McRae and Fryer, Tjensvold,

Feix, Phillips & Lempio 57] ABSTRACT Clutch mechanism for coupling anengine to a transmission of the form in which ratio gears are decoupledfrom both the driving and driven shafts and braked to a stop tofacilitate shifting has epicyclic gear means for imparting apredetermined slow rotation to the ratio gears just prior to fullrecoupling of the ratio gears to the driving engine and driven load.This assures that all necessary gear engagements are accomplishedsmoothly and without damage prior to the reapplication of full torqueload to the transmission.

10 Claims, 6 Drawing Figures 1 l l I a i t .PATENTEDJUH 5191s SHEET 1[1F 5 PATENTEDJUH 5192s 3.736.814

SHEET 3 [IF 5 BACKGROUND OF THE INVENTION This invention relates toinput clutches for disposition between a driving engine and a multispeedtransmission and more particularly to torque input clutches fortransmissions of the form in which change speed gears are momentarilybraked to a stop to facilitate shifting.

A common type of transmission for coupling an engine to driven meanssuch as the wheels of a vehicle has a plurality of change speed or ratiogears which may be shifted to provide a selected one of several driveratios. In the more conventional form such transmissions are used withan input clutch for disconnecting the engine from the change speedgearing during the course of a shift. In this more conventional form ofsuch transmissions, the output member of change speed gearing remainsconnected to the rotating driven load and thus it is necessary toprovide synchronizers within the gearing system to facilitate shifting.The synchronizers have the undesirable effect of adding to bulk,complexity and maintenance problems in the transmission. As a practicalmatter, the need for synchronizers has the further effect of limitingthe number of drive ratios obtainable with a given set of ratio gears toa number smaller than the theoretical number of different power pathsthere through.

U.S. Pat. No. 3,508,450 discloses a form of transmission in whichsynchronizers are not needed and thus the problems discussed above arealleviated. In the transmission of U. S. Pat. No. 3,508,450, a clutch isprovided at both the input and output ends of the change speed gearing,together with means for braking the gears, so that the desired shiftingcan be accomplished with the gears in a stationary or near stationarycondition. At the conclusion of the shift transient, the shifted gearsare then reaccelerated and recoupled to both the driving engine anddriven load.

In a transmission of the last discussed type there is a possibility thatthe braked change speed gears may come to rest in a position at whichtooth abuttment occurs when shifting is attempted. This condition iscorrected, so that gear engagement may proceed, when the gearing beginsto reaccelerate at the end of the shift transient. However, theextremely rapid and forceful reacceleration which occurs when the inputclutch reengages may be too fast for this purpose. Accordingly, US Pat.No. 3,508,450 discloses a form of roll-over means which imparts a slowrotation to the change speed gearing, to assure gear engagement, priorto the time that the input clutch reengages to apply full engine torqueto the gearing. In particular, prior US. Pat. No. 3,508,450 teaches afriction disc means operative between a portion of the input clutchwhich remains rotating when the clutch is disengaged and the input tothe change speed gearing. The brake which holds the change speed gearingstationary during the shift transient is released slightly before theinput clutch reengages and thus a limited amount of torque istransmitted to the change speed gearing by the friction disc for a briefinterval to provide the desired slowlyaccelerating, roll-over motion.

The friction disc roll-over means described above is highly sensitive tovariations in the viscosity of the lubricating medium in the inputclutch and to slight dimensional changes resulting from wear ortemperature variations. As a consequence, the timing of roll-over motionand the amount of torque transmitted to the change speed gears forroll-over purposes varies undesirably. Further, the speed of theroll-over motion cannot be precisely predetermined nor kept constantunder varied operating conditions. Wear of the ratio gears is therebydecreased and tooth breakage may occur.

SUMMARY OF THE INVENTION The present invention provides an input clutchfor a transmission of the form described above having a rollovermechanism in which both the timing and the speed of the roll-over motionin the change speed gearing is more reliably controlled.

A pair of sun gears are used for this purpose, a first of which iscoupled to the change speed gears for rotation therewith with the secondbeing supported for rotation relative thereto. Epicyclic gear means,which rotates in both the engaged and disengaged condition of the inputclutch is coupled to both sun gears with a slightly different driveratio with respect to each sun gear. Thus if one of the sun gears isforcibly stopped the other is constrained to rotate slowly. The inputclutch includes brake means which stops the change speed gears duringthe initial portion of the shift transient and thereby also stops thefirst sun gear causing the second sun gear to rotate. The brake meansreleases the first sun gear towards the end of the shift period andstops the second sun gear causing the first sun gear to rotate and turnthe change speed gearing with the desired slow roll-over motion.

Accordingly, it is an object of this invention to facilitate theshifting of transmissions of the form having change speed gears whichare brought to a stationary or near stationary condition for shiftingpurposes.

It is a further object of the invention to provide an input clutch forcoupling an engine to a multispeed transmission of the form havingchange speed gears which are brought to a stationary or a nearstationary condition for shifting, wherein a relatively slow rotationalmotion is imparted to the change speed gears at the conclusion of shiftperiod with precise timing and at a predetermined speed.

It is still another object of this invention to reduce wear and the riskof gear tooth damage in transmissions of the form described above.

The invention, together with further objects and advantages thereof,will best be understood by reference to the following description ofpreferred embodiments taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a partially broken out side elevation view of a vehicletransmission having an input clutch in accordance with the invention,

FIG. 2 is a side view, partially broken out and partially in axialsection, of the input clutch depicted in FIG. 1,

FIG. 3 is a staggered crosssection view taken along line Ill-III of FIG.2,

FIG. 4 is a graphical illustration of variations of speed as a functionof time of certain elements of the apparatus of FIGS. 1 to 3 during thecourse of a shift transient,

FIG. 5 is a side view, partially broken out and partially in axialsection, of a modified form of the input clutch, and

FIG. 6 is a staggered cross-section view taken along line VI-VI of FIG.5.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring initially to FIG. 1 ofthe drawing, an input clutch assembly 11 in accordance with theinvention is coupled between an engine 12 which may be of conventionalform and a transmission 13 of the form described in U.S. Pat. No.3,508,450. In order to facilitate understanding of the functions of theclutch assembly 11, certain significant characteristics of thetransmission 13 will be briefly described, reference being made to U.S.Pat. No. 3,508,450 for suitable detailed description of such atransmission. Such a transmission 13 has an input shaft 14 whichreceives torque from the driving engine 12 through the input clutchassembly 1 l and has an output flange 16 to which torque is deliveredfor driving a rotary load such as the wheels of a vehicle. Atransmission 13 of this form contains a plurality of change speed gearsof which two such gears 17 and 18 are shown in FIG. 1. Any selected oneof a plurality of drive ratios between input shaft 14 and output flange16 may be established by shifting the pattern of engagements between theseveral change speed gears. In this example gears, such as gears 17 and18, may be selectively engaged or disengaged by axial movement of aninternally toothed annular clutch collar 19 splined to one of the twogears, such as gear 17 in this instance. Axial movement of clutch collar19 towards gear 18 causes the collar to engage both gears 17 and 18 andthereby establish a driving connection therebetween. As described inU.S. Pat. No. 3,508,450, the transmission 13 contains additional gearpairs and clutch collars 19 in order to establish any selected one of aplurality of drive ratios.

To shift the appropriate ones of the clutch collars 19 in response tomovement of an operators control lever 21 between the various speedsettings thereof, a pneumatic control circuit 22 actuates predeterminedones of a series of fluid pressure operated cylinder 23 to manipulateshift forks 24 which engage the clutch collars 19. Control circuit 22may be of the form described in detail in U.S. Pat. No. 3,570,636 andreference should be made thereto for a description of the detailedstructure and operation of a suitable pneumatic control circuit.

It may be observed in FIG. 1 that in contrast to more conventionaltransmissions of this general class, no synchronizers are provided tofacilitate engagement of the internal teeth of clutch collar 19 with theexternal teeth of change speed gear 18. Instead, input clutch assembly11 responds to a pneumatic signal indicative of movement of the operatorshift lever 21 from one speed setting to another by first decouplingtransmission shaft 14 from engine 12 and then braking the input shaft tostop rotation of the change speed gears which are coupled thereto. Thetransmission 13 has an output clutch assembly 26 which also responds tosuch signal by decou pling the output flange 16 from the change speedgears.

Accordingly, with the change speed gears such as gears l7 and 18momentarily stopped, the need for conventional synchronizers iseliminated. After pneumatic cylinders 23 have been actuated by controlcircuit 22 to shift the appropriate clutch collars 19, input clutchassembly 11 effects a modulated recoupling of engine 12 to transmissioninput shaft 14 and output clutch 26 reengages to reestablish drivethrough the transmission 13 at'the newly selected drive ratio.

By thus stopping the change speed gears during the course of a shift theneed for conventional synchronizers is avoided. However with the gears,such as gears 17 and 18, stopped in this manner it may not be possibleto immediately shift clutch collar 19 to engage ears l7 and 18 if therotational position of the clutch collar relative to gear 18 is suchthat tooth abutment occurs. Under this circumstance, the desiredengagement is not effected until gear 18 again begins to rotate andthereby brings the two sets of teeth into a suitable relationship forengagement. It is not desirable to rely upon the recoupling oftransmission input shaft 14 to engine 12 through input clutch assembly11 at the end of the shift cycle for this purpose. The resultantacceleration of gear 18 at that time is extremely rapid. As aconsequence, the engagement of clutch collar 19 with gear 18 could beeither too abrupt or might not occur at all causing severe shocks,excessive tooth wear and the risk of tooth breakage.

Accordingly in this form of transmission it is preferable to provide fora relatively slow rotation of the transmission input shaft 14 just priorto the time that input clutch 1'1 reengages and applies the full torqueof engine 12 thereto. Heretofore, as described in U.S. Pat No. 3,508,450for example, this has been accomplished through friction disc meanswhich transmits a limited amount of torque from engine 12 to input shaft14 while the clutch 11 is still in the disengaged condition. Suchfriction drives do not provide for a precise predetermined rotation ofinput shaft 14 but are subject to considerable variation in the speedand timing of input shaft rotation due to such causes as temperaturechanges, variations in viscosity of the lubricating medium, and wear.

The input clutch 11 of the present invention alleviates these problemsby providing for precisely timed roll-over of the transmission inputshaft 14 at a predetermined speed, relative to engine 12, just prior totransmission of full engine torque through the input clutch.

Referring now to FIG. 2, certain components of input clutch assembly 11are essentially similar to those of the input clutch mechanism describedin co-pending application Ser. No. 30,680 now U.S. Pat. No. 3,667,583for Elmer A. Richards for SELF- MODULATED INPUT CLUTCH FOR VEHICLE DRIVETRANSMISSIONS, filed Apr. 22, 1970 and assigned to the Assignee of thepresent application. Basically, an input clutch assembly of this formmay have a main shaft which is the output member and which may simply bea forward extension of the input shaft 14 of transmission 13 where theclutch assembly is formed integrally with the transmission as anessentially unitary mechanism therewith as described in co-pendingapplication Ser. No. 30,680. The drive input member of the clutchassembly may be the engine flywheel 28 which is coaxial with respect tothe forward end of main shaft 14 with a bearing 29 being disposedtherebetween. Flywheel 28 has a rearwardly extending annular sleeveportion 31 to which an annular input member 32 is secured for rotationwith the flywheel. An annular driven hub 33 is 'splined to main shaft 14radially inward from input member 32.

When the clutch assembly 11 is engaged input member 32 transmits drivefrom flywheel 28 to driven hub 33 through a pack 34 of annular clutchplates of which alternate ones are splined to the input member 32 andthe intervening ones are splined to driven hub 33. To apply pressure toclutch pack 34 when the clutch assembly 11 is to be engaged, an annularpressure plate 36 is disposed co-axially with respect to shaft 14forwardly from driven hub 33. Pressure plate 36 is movable in an axialdirection and may be caused to bear against the forward end of clutchpack 34 to compress the clutch pack against input member 32 therebycausing torque to be transmitted from flywheel 28 to shaft 14.

Considering now the means through which the clutch assembly 11automatically performs the engagement, disengagement and modulationfunctions which customarily require operator control by means of aclutch pedal or the like, an annular axially movable capacity modifyingplate 37 is situated between flywheel 28 and pressure plate 34 withinthe sleeve portion 31 of the flywheel. An annular seal 38 is mounted inthe rim of modifying plate 37 to provide a fluid tight seal with theadjacent inner surface of flywheel sleeve 31 whereby when the flywheelis rotated by the associated engine, a volume of lubricating fluid suchas oil 39 is trapped between the flywheel and modifying plate bycentrifugal force which tends to cause the fluid to move radiallyoutward with respect to the rotary axis of the system. The rotatingvolume of oil 39 trapped in this manner by centrifugal force exerts anaxial force against modifying plate 37 tending to urge plate 37 in thedirection of pressure plate 36 with the magnitude of such force being afunction of the rotational speed of flywheel 28. This variable forcecauses disengagement of the clutch at idling speeds and a modulatedreengagement as speed is increased through an intermediate range.

For this purpose a series of engagement springs 41 act between modifyingplate 37 and pressure plate 36 and a series of disengagement springs 42act between the modifying plate and input member 32. Disengagementsprings 42 thus tend to resist the force of fluid 39 against modifyingplate 37 and at low engine speeds are able to hold the modifying platein the forward position adjacent to flywheel 28. At this position of themodifying plate 37, engagement springs 41 do not transmit anysignificant force from the modifying plate to pressure plate 36.Accordingly under this condition the clutch pack 34 is not compressedand torque is not transmitted from flywheel 28 to shaft 14. As enginespeed is increased, the force of fluid 39 begins to overcome springs 42and the modifying plate 37 shifts rearwardly. Such motion of themodifying plate 37 causes engagement springs 41 to exert an increasingforce against pressure plate 36 and thus an increasing force is exertedagainst clutch pack to produce the modulated engagement wherein theclutch capacity is a function of engine speed thereby duplicating theconventional actions of a human operator in controlling the clutch pedalof a vehicle.

While the modulated reengagement described above is desirable atintermediate engine speeds, the clutch capacity should be heldsubstantially constant at higher engine speeds. Accordingly, an annularstop 43 extends forward from input member 32 to block further backwardmotion of modifying plate 37 after the engine speed reaches thepredetermined value at which the clutch capacity versus engine speedcurve should flatten out. Once modifying plate 37 abuts stop 43, thepressure of fluid 39 no longer causes a variation of the clutch capacitywhich is then determined solely by the engagement springs 41.

In order to accomplish a shift of the transmission, it is necessary thatthe input clutch assembly 11 be disengaged without regard to enginespeed at the beginning of the shift transient. In order to override theself modulating action described above to force disengagement of theclutch at the beginning of the shift transient without regard to thepressure of fluid 39, an annular piston 44 is slideable within a cavity46 at the back wall of the housing 47 of the clutch assembly and may beforced forwardly by admission of compressed air into cavity 46 through aconduit 48 communicating with the pneumatic control circuit. Suchforward motion of piston 44 is transmitted to pressure plate 36 througha needle bearing 49 disposed between the piston and axially slideablepins 51 transpierced through an annular brake hub 52. Pins 51 in turnbear against an axially slideable annular element 53 which exerts aforce against the ends of an additional set of axially slideable pins 56transpierced through driven hub 33. Springs 54 between element 53 andpins 56 maintain proper race contact of thrust bearings 49 and 57 whenpiston 44 is not pressurized. The opposite ends of pins 56 bear againstthe pressure plate 36 through an additional needle bearing 57. Thusforward motion of piston 44 forces disengagement at clutch pack 34 byforcing the pressure plate 36 forwardly. Release of the air pressuresignal within chamber 46 at the conclusion of the shift transientenables the self-modulating mechanism described above to reassumecontrol of the pressure on the clutch pack.

As pointed out above, in a transmission of the particular form withwhich the clutch assembly 11 is employed, release of the clutch pack 34at the beginning of the shift transient must be accompanied by brakingof the shaft 14 in order to stop the change speed gears in thetransmission. For this purpose, the brake hub 52 is splined to shaft 14and alternate ones of a series of brake discs 58 are splined to the rimof the brake hub and situated within a cavity 59 formed by a forwardlyextending sleeve 61 secured to the back wall of the housing 47. Sleeve61 has an annular inwardly extending member 62 against which the brakediscs 58 may be compressed by forward movement of a brake piston 63 incavity 59 in response to the admission of pressurized air into the backportion of the cavity through a conduit 64 connecting with the pneumaticcontrol circuit. At least one of the brake discs 58, situated betweendiscs which are splined to brake hub 52, is splined to the inner wall ofsleeve 61. Thus forward movement of brake piston 63 compresses the discs58 against member 62 thereby stopping rotation of brake hub 52. Thisstops rotation of the transmission gears by stopping shaft 14.

The structure and operation of clutch assembly 11 as described to thispoint is basically similar to that described in the above identifiedco-pending application Ser. No. 30,680. Considering now the novel meansof the present invention by which a predetermined slow rotation of shaft14 is effected, prior to engagement of clutch pack 34 at the conclusionof the shift transient, reference should be made to FIGS. 2 and 3 inconjunction. An annular internally toothed ring gear 66 is formedintegrally on the back surface of input member 32 and is coaxial withshaft 14. A first sun gear 67 of substantially less diameter than ringgear 66 is formed integrally on driven hub 33. A second adjacent sungear 68 is formed on an annular member 69 which is rotatively supportedon brake hub 52. The teeth of first and second sun gears 67 and 68 areof substantially less axial length than the teeth of ring gear 66 andthe two sets of teeth are adjacent whereby a pair of planetary gears 71,disposed at diametrically opposite positions relative to the sun gears,may be engaged with ring gear 66 and both sun gears simultaneously. Ringbear 66, planetary gear 71 and sun gears 67 and 68 thus constitute anepicyclic gear means which is capable of transmitting torque from inputmember 32 to shaft 14 independently of clutch pack 34 under certainconditions to be hereinafter described.

As will be discussed in more detail, control of the action of theepicyclic gear means is effected in part by selective braking of thesecond sun gear 68. For this purpose an annular brake plate 72 issplined to member 69 and extends radially outward adjacent the forwardface of member 62 of sleeve 61. Brake member 72 may be compressedagainst sleeve member 62, to apply a braking force to the second sungear 68, by application of a pressurized air signal to still anothercavity 74 in housing back wall 47 through a conduit 76 connecting withthe pneumatic control circuit. A piston 77 in cavity 74 is therebyforced forward causing a rod 78 which extends forward from the piston topivot a rocker arm 79 about a bolt 81 which holds the rocker arm againstthe forward surface of housing element 61. This causes rocker arm 79 tourge a shoe 82 against the forward face of brake member 72 therebycompressing the brake member against sleeve member 61 to exert a lightbraking force on second sun gear 68 through members 72 and 69.

Referring now to FIG. 3 in particular, which is a staggered crosssection view through the clutch assembly and thus shows a portion of thefirst sun gear 67 in the lower half of the figure and a portion of thesecond sun gear 68 in the upper half of the figure, an important aspectof the invention is that the two sun gears have slightly differing driveratios with respect to the planetary gears 71 which engage both sungears. This is accomplished, in this example of the invention, byproviding the second sun gear 68 with fewer teeth than first sun gear67. In one example of the invention, the ring gear 66 has 90 internalteeth 66a, the two planetary gears 71 each have 15 teeth 710, whilefirst sun gear 67 has 60 teeth 67a and second sun gear 68 has 58 teeth68a. Accordingly if one of the sun gears is held stationary while ringgears 66 rotates, the other of the sun gears is forced by planetarygears 71 to undergo a slow rotation wherein the speed reduction ratiorelative to flywheel 28 in the particular example described above isapproximately 50:]. The necessary modifications of standard gear teethto enable two gears of substantially the same diameter but havingdifferent number of teeth to be jointly engaged and driven by anothergear are known to the art and are described in detail, for example, in apaper entitled Modifying Standard Proportions of Involute Gears" by C.H. Herr published in the SAE Journal, November 1949, pages 19 to 23.Basically, this is accomplished by changing the tooth profile on one ofthe driven gears to extend the effective pitch diameter of the one gearwithout necessarily changing the overall diameter.

Considering now the operation of the roll-over mechanism describedabove, with reference to FIGS. 2 and 4 in conjunction, during theengaged condition of clutch assembly 11 shaft 14 is effectively coupledto flywheel 28 through clutch pack 34. First sun gear 67 is therebyconstrained to rotate in synchronism with ring gear 66. Under thiscondition, the planetary gears 71 are held against rotation about theirown axes and are orbited around shaft 14. Since there is no rotation ofplanetary gears 71 about their own axes, sun gear 68 is locked to sungear 67, and rotates at the same speed. Inasmuch as brake shoe 82 isreleased from brake plate 72 at the time, it has no effect on thetransmission of torque through the clutch assembly 11.

When a shift transient begins, brake piston 44 is advanced as previouslydescribed to disengage the clutch assembly 11 at clutch pack 34.Simultaneously, piston 63 is advanced to brake shaft 14 as previouslydescribed, and piston 77 is also advanced at the time to cause shoe 82to apply braking pressure to brake plate 72 and thus to the second sungear 68. As shown in FIG. 4, the speed of shaft 14 rapidly decreases tostop the change speed gears in the transmission. At this point in theshift cycle, ring gear 66 continues to turn as it is secured to flywheel28; however, first sun gear 67 is now stopped as it is coupled to shaft14. Planetary gears 71 are therefore forced to rotate about their ownaxes in addition to orbiting about the axis of shaft 14. This in turnforces rotation of second sun gear 68, notwithstanding the light brakingpressure applied at shoe 82. With shaft 14 stopped, the previouslydescribed pneumatic actuators 23 of the transmission are actuated toattempt the change of gear engagements which are necessary foraccomplishing the desired shift of the transmission.

At the next stage in the shift transient, the pneumatic control circuitreleases pressurized air from behind brake piston 63, thereby removingthe braking force which was applied to shaft 14. Pressure is momentarilymaintained in cavity 74 so that the light braking force of shoe 82against brake plate 72 is temporarily continued after shaft 14 has beenreleased for rotation.

At this point, brake shoe 82 is enabled to stop rotation of the secondsun gear 68 inasmuch as the first sun gear 67 is now able to rotate toaccommodate to the different drive ratios of the two sun gears relativeto the ring gear. Thus, at this point the planetary gears 71 now walkaround the stationary second sun gear 68, forcing a small predeterminedamount of rotation of first sun gear 67 and shaft 14 as shown in FIG. 4.This is the desired slow rollover rotation of shaft 14 which assuressmooth engagement of change speed gears in the transmISSIOI'I.

To conclude the shift transient, the pneumatic control circuit releasespressurized air from behind brake pistons 44 and 77. This initiates theself-modulated reengagement of the clutch assembly 11 at clutch pack 34as previously described, and releases the pressure of brake shoe 82against brake plate '72 so that the second sun gear 68 may again rotatesynchronously with ring gear 66 and the first sun gear 67.

While the embodiment of the invention described above utilizes a secondsun gear 68 having fewer teeth than first sun gear 67 whereby therollover motion of the shaft 14 is in the same angular direction as thenormal rotation of the shaft during the engaged condition of the clutch,it is also possible to provide the first sun gear 67 with fewer butmodified teeth relative to standard teeth carried on a second sun gear68. With such a modification, the rollover motion will then be counterto the normal direction of rotation of shaft 14 but will still providethe desired result of facilitating engagement of change speed gears atthe conclusion of the shift transient.

Referring now to FIGS. and 6 in conjunction another embodiment of theinput clutch assembly 11' is shown wherein a different form of epicyclicgearing is used to provide the desired rollover motion of the main shaft14 at the conclusion of a shift transient.

Aside from the rollover mechanism, the general construction of clutchassembly is similar to that of the first embodiment and accordingly willnot be redescribed, elements of clutch assembly 11' which are similar tothose of the first embodiment being designated in FIGS. 5 and 6 bysimilar reference numerals differentiated by a prime mark.

Considering now the modified rollover mechanism, the first and secondsun gears 67' and 68' respectively may be similar to those of thepreviously described embodiment but are driven by direct engagement witha modified ring gear 84 carried on input member 32' rather than throughplanetary gears as in the previously described embodiment. As best seenin FIG. 6, this is accomplished by mounting the ring gear 84eccentrically on input member 34' whereby the geometrical center 86 ofthe ring gear is displaced from the rotary axis 87 of the input member32' and sun gears 67 and 68'. Ring gear 84 is supported in this positionby disposition within a sleeve 88 formed integrally on the input member32', an annular bearing 89 being situated between the ring gear andsleeve to provide for relative rotation therebetween. Owing to theeccentric position of ring gear 84 relative to the two sun gears 67' and68', the ring gear teeth engage the teeth of the two sun gears at alimited circumferential zone thereon which zone orbits around the rotaryaxis 87 as the input member 32' revolves.

Since as in the previously described embodiment, the two sun gears 67'and 68' have differing number of teeth, but are both engaged with anddriven by the same gear means, stopping of one sun gear necessarilyforces rotation of the other. Accordingly the eccentrically placed ringgear 84 acts on the two sun gears 67' and 68' in a manner similar to theaction of the ring gear and planetary gears of the first describedembodiment thereon and the operation of the clutch assembly 11 isotherwise similar to that of the first described clutch assembly 11.

While invention has been described with respect to certain preferredembodiments, it will be apparent that still other modifications arepossible and thus it is not intended to limit the invention except asdefined in following claims.

What is claimed is:

l. A clutch assembly for transmitting torque from an engine to thechange speed gears of a transmission wherein said change speed gears aredecoupled from said engine and braked to facilitate shifting, comprismg:

a rotary drive input member having means for connection to said engine,

a rotary drive output member having means for connection to said changespeed gears of said transmission,

clutch means having an engaged condition for transmitting drive fromsaid input member to said output member and having a disengagedcondition,

a first sun gear coupled to said output member for rotation therewith,

a second sun gear supported for rotation relative to said output member,

epicyclic gear means driven by said input member and engaging each ofsaid sun gears and providing a drive ratio between said input member andsaid first sun gear which differs from the drive ratio provided betweensaid input member and said second sun gear whereby immobilization of onesaid sun gears forces rotation of the other thereof, and

second sun gear brake means for impeding rotation of said second sungear while said clutch means is disengaged to cause said first sun gearto rotate said output member.

2. A clutch assembly as defined in claim 1, further comprising outputmember brake means for braking rotation of said output member while saidclutch means is disengaged during an initial portion of the period inwhich said transmission change speed gears are shifted, and wherein saidsun gear brake means applies a lesser braking force to said second sungear than said output member brake means applies to said output memberwhereby said sun gear brake means slips to allow rotation of said secondsun gear while said output member brake means is applied andsubsequently stops said second sun gear when said output member brakemeans is released.

3. A clutch assembly as defined in claim 1 further comprising a fluidpressure driven piston for actuating said second sun gear brake means.

4. A clutch assembly as defined in claim 1 wherein said first and secondsun gears have substantially the same diameter and wherein one sun gearhas a different number of gear teeth than the other and a differenteffective pitch diameter than the other in order to provide saiddifferent drive ratios.

5. A clutch assembly as defined in claim 4 wherein said first and secondsun gears are disposed in an adjacent coaxial relationship and wherein asingle set of teeth carried by said epicyclic gear means engages saidteeth of both of said sun gears.

6. A clutch assembly as defined in claim 1 wherein said epicyclic gearmeans comprises a ring gear supported on said input member in coaxialrelation thereon and having internal teeth, and at least one planetarygear disposed between said ring gear and said sun gear, said planetarygear having teeth engaging said teeth of said ring gear and engagingsaid teeth of both of said sun gears.

7. A clutch assembly as defined in claim 1 wherein said epicyclic gearmeans comprises an annular ring gear supported on said input member forrelative rotation with respect thereto and having gear teeth, said ringgear being positioned eccentrically with respect to said input memberwhereby said teeth of said ring gear engage teeth of both said sun gearsalong a limited zone of the circumference of said sun gears which zoneorbits around the rotational axis of said sun gears and said inputmember as said input member rotates.

8. In clutch assembly for disposition between an engine and atransmission gear box of the form wherein change speed gears aredisconnected from said engine and braked to facilitate shifting,comprising, in combination:

a clutch housing,

an input member rotatable relative to said clutch housing and havingmeans for connection to said engine to be driven thereby,

a rotatable output shaft extending along the axis of said input memberwithin said housing and journailed for rotation therein,

an annular driven hub coupled to said output shaft for rotationtherewith,

a plurality of annular coaxial clutch discs, at least one being splinedto said input member and at least another one being splined to saiddriven hub,

means for applying axial pressure against said plurality of clutch discsfor establishing a driving relationship between said input member andsaid driven hub,

a first toothed sun gear disposed coaxially with respect to said drivenhub for rotation therewith,

a second toothed sun gear disposed adjacent said first sun gear incoaxial relationship therewith for rotation relative thereto, saidsecond sun gear being of substantially the same diameter as said firstsun gear but having a number of teeth which differs from the number ofteeth on said first sun gear,

epicyclic gear means including a ring gear supported on said inputmember and rotated thereby, said epicyclic gear means having at leastone set of teeth which engages the teeth of both of said sun gearstransmitting drive from said input member to both of said sun gears,said differing number of teeth on said sun gears establishing adifferent drive ratio between said first sun gear and said input memberand said second sun gear and said input member whereby stopping of oneof said sun gears necessitates rotation of the other thereof,

at least one brake member coupled to said second sun gear for rotationtherewith,

first brake means for stopping rotation of said output shaft when saidpressure on said plurality of clutch discs is released to disengage saidclutch assembly, and

second brake means for applying pressure to said brake member to stoprotation of said second sun gear when said first brake means isreleased.

9. The combination defined in claim 8 wherein said ring gear is securedto said input member in coaxial relationship thereon, and wherein saidepicyclic gear means further comprises at least one planetary gearengaging said ring gear and both of said sun gears.

10. The combination defined in claim 8 wherein said ring gear iseccentrically positioned relative to said input member and is supportedthereon for rotation relative thereto, and wherein said ring gear isengaged with both of said sun gears at a limited zone of thecircumference thereof.

1. A clutch assembly for transmitting torque from an engine to thechange speed gears of a transmission wherein said change speed gears aredecoupled from said engine and braked to facilitate shifTing,comprising: a rotary drive input member having means for connection tosaid engine, a rotary drive output member having means for connection tosaid change speed gears of said transmission, clutch means having anengaged condition for transmitting drive from said input member to saidoutput member and having a disengaged condition, a first sun gearcoupled to said output member for rotation therewith, a second sun gearsupported for rotation relative to said output member, epicyclic gearmeans driven by said input member and engaging each of said sun gearsand providing a drive ratio between said input member and said first sungear which differs from the drive ratio provided between said inputmember and said second sun gear whereby immobilization of one said sungears forces rotation of the other thereof, and second sun gear brakemeans for impeding rotation of said second sun gear while said clutchmeans is disengaged to cause said first sun gear to rotate said outputmember.
 2. A clutch assembly as defined in claim 1, further comprisingoutput member brake means for braking rotation of said output memberwhile said clutch means is disengaged during an initial portion of theperiod in which said transmission change speed gears are shifted, andwherein said sun gear brake means applies a lesser braking force to saidsecond sun gear than said output member brake means applies to saidoutput member whereby said sun gear brake means slips to allow rotationof said second sun gear while said output member brake means is appliedand subsequently stops said second sun gear when said output memberbrake means is released.
 3. A clutch assembly as defined in claim 1further comprising a fluid pressure driven piston for actuating saidsecond sun gear brake means.
 4. A clutch assembly as defined in claim 1wherein said first and second sun gears have substantially the samediameter and wherein one sun gear has a different number of gear teeththan the other and a different effective pitch diameter than the otherin order to provide said different drive ratios.
 5. A clutch assembly asdefined in claim 4 wherein said first and second sun gears are disposedin an adjacent coaxial relationship and wherein a single set of teethcarried by said epicyclic gear means engages said teeth of both of saidsun gears.
 6. A clutch assembly as defined in claim 1 wherein saidepicyclic gear means comprises a ring gear supported on said inputmember in coaxial relation thereon and having internal teeth, and atleast one planetary gear disposed between said ring gear and said sungear, said planetary gear having teeth engaging said teeth of said ringgear and engaging said teeth of both of said sun gears.
 7. A clutchassembly as defined in claim 1 wherein said epicyclic gear meanscomprises an annular ring gear supported on said input member forrelative rotation with respect thereto and having gear teeth, said ringgear being positioned eccentrically with respect to said input memberwhereby said teeth of said ring gear engage teeth of both said sun gearsalong a limited zone of the circumference of said sun gears which zoneorbits around the rotational axis of said sun gears and said inputmember as said input member rotates.
 8. In clutch assembly fordisposition between an engine and a transmission gear box of the formwherein change speed gears are disconnected from said engine and brakedto facilitate shifting, comprising, in combination: a clutch housing, aninput member rotatable relative to said clutch housing and having meansfor connection to said engine to be driven thereby, a rotatable outputshaft extending along the axis of said input member within said housingand journalled for rotation therein, an annular driven hub coupled tosaid output shaft for rotation therewith, a plurality of annular coaxialclutch discs, at least one being splined to said input member and atleast another one being splined to said driven hub, means for applyingaxial pressure against said plurality of clutch discs for establishing adriving relationship between said input member and said driven hub, afirst toothed sun gear disposed coaxially with respect to said drivenhub for rotation therewith, a second toothed sun gear disposed adjacentsaid first sun gear in coaxial relationship therewith for rotationrelative thereto, said second sun gear being of substantially the samediameter as said first sun gear but having a number of teeth whichdiffers from the number of teeth on said first sun gear, epicyclic gearmeans including a ring gear supported on said input member and rotatedthereby, said epicyclic gear means having at least one set of teethwhich engages the teeth of both of said sun gears transmitting drivefrom said input member to both of said sun gears, said differing numberof teeth on said sun gears establishing a different drive ratio betweensaid first sun gear and said input member and said second sun gear andsaid input member whereby stopping of one of said sun gears necessitatesrotation of the other thereof, at least one brake member coupled to saidsecond sun gear for rotation therewith, first brake means for stoppingrotation of said output shaft when said pressure on said plurality ofclutch discs is released to disengage said clutch assembly, and secondbrake means for applying pressure to said brake member to stop rotationof said second sun gear when said first brake means is released.
 9. Thecombination defined in claim 8 wherein said ring gear is secured to saidinput member in coaxial relationship thereon, and wherein said epicyclicgear means further comprises at least one planetary gear engaging saidring gear and both of said sun gears.
 10. The combination defined inclaim 8 wherein said ring gear is eccentrically positioned relative tosaid input member and is supported thereon for rotation relativethereto, and wherein said ring gear is engaged with both of said sungears at a limited zone of the circumference thereof.